1. Field of the Invention
The invention relates to a damping valve body of the type having an axis, a circumference, first passages for flow in a first axial direction, and second passages for flow in a second axial direction, each passage having a boundary wall extending between an inlet opening and an outlet opening, at least some of said outlet openings being covered by a valve disk.
2. Description of the Related Art
U.S. Pat. No. 4,830,152 discloses a damping valve in the form of a piston damping valve having passages for a damping fluid, at least some of the passages having a circumferentially extending outlet opening that is at least partially covered by at least one valve disk. The significant advantage of circumferentially extending passages or at least outlet openings is that a larger outlet cross section can be achieved and this, in turn, gives the damping valve a somewhat degressive damping-force characteristic. The piston damping valve in U.S. Pat. No. 4,830,152 is composed of a sintered material and can therefore be designed with considerably more freedom than a damping valve that is formed in a disk shape, in one piece and by stamping, where, starting from a damping-valve main body, those areas of the damping-valve body which are raised on one side of the damping valve are in the form of depressions on the axially opposite side of the damping valve. Damping valves constructed in this way have been disclosed in U.S. Pat. Nos. 5,615,756, 6,018,868, and 6,129,005, for example, and have a plurality of passages with a circular cross section. Overall, the sum of the cross-sectional areas of the outlet openings is significantly less than with a damping valve corresponding to U.S. Pat. No. 4,830,152. It is not possible simply to transfer the configuration of the passages to a damping valve produced by means of stamping since there is a limit to the forming that can be performed by stamping and, for example, the annular chamber illustrated in FIG. 1 can be formed only with difficulty in a stamped damping valve.
It is the object of the present invention to obtain a damping valve that allows a degressive damping-force characteristic at a low overall damping-force level.
According to the invention, the object is achieved by virtue of the fact that the circumferentially extending outlet opening has a rib that extends radially, relative to a first direction of flow of the damping fluid, from a boundary wall of the outlet opening and bears a valve support surface for the at least one valve disk.
The circumferentially extending outlet opening allows better use of the damping valve""s area as regards maximization of the area subjected to pressure on the valve disks used. The larger the outlet openings can be made, the more degressive the damping-force characteristic can be made and the lower the damping-force level that can be achieved. If the intention is to make the damping-force characteristic less degressive or to achieve higher damping-force levels, it is possible to use thicker valve disks, which have a higher fatigue strength.
In a further advantageous refinement, the rib is designed as a rib extension. Two advantages are achieved by means of this measure. On the one hand, it results in a weaker restriction effect in the passage and, in addition, a particularly light damping-valve body is obtained.
In order to achieve as uniform as possible a distribution of the areas of support for the valve disks, the rib is embodied so as to extend radially inward from an outer boundary wall of the outlet opening. The rib can also be made to extend radially outward from an inner boundary wall of the outlet opening but production of such a rib arrangement in conjunction with trapezoidal outlet openings is less advantageous since the lateral clearance for a tool between the rib and the lateral end points of the inner boundary wall should be as large as possible.
In order to come even closer to achieving as uniform as possible distribution of the area of support, provision is made for at least one valve support surface to be arranged radially relative to an area in which the circumferentially extending outlet openings are formed, this valve support surface being arranged on a radial reference line that coincides with the rib.
Production of the damping-valve body is particularly simple if the outlet opening in the damping-valve body has the same cross section as an inlet opening of the same passage.
Thus, there is provision for the damping-valve body to be formed in a disk shape, in one piece and by stamping, and, starting from a damping-valve main body, those areas of the damping-valve body which are raised on one side of the damping valve are in the form of depressions on the axially opposite side of the damping valve. Essentially perpendicular punched and stamped surfaces are advantageous, particularly in this production process.
Particularly good support for the valve disk can be achieved if the outlet opening is framed by a valve support surface embodied as an encircling ridge.
In order to maximize the effective area subjected to pressure on the valve disk as far as possible, provision is made for the encircling ridge of the outlet opening for the first direction of flow to extend radially outside the area of the main body of the damping valve that bears the valve support surface for the valve disk of the second direction of flow on the rear side of the rib.
Other objects and features of the present invention will become apparent from the following detailed description considered in conjunction with the accompanying drawings. It is to be understood, however, that the drawings are designed solely for purposes of illustration and not as a definition of the limits of the invention, for which reference should be made to the appended claims. It should be further understood that the drawings are not necessarily drawn to scale and that, unless otherwise indicated, they are merely intended to conceptually illustrate the structures and procedures described herein.